1. Technical Field
This invention relates to image processing and, more particularly, to techniques for determining a positive aimpoint on an object moving through heavy background clutter.
2. Discussion
One of the most important factors in the design of a guidance system is the determination of a suitable final aimpoint on the object of interest (target). It is usually necessary to pinpoint a vital part on the object since a near miss or a hit on a noncritical part will not accomplish the objectives of the task. For example, if the objective of a guidance system is to position a drill so that a hole can be drilled at a specific spot (aimpoint) of a workpiece, it is absolutely vital that the aimpoint be precisely identified.
For the purposes of this discussion, we will assume a tracker is on a moving platform and is used to direct the platform (seeker) toward a specified point on the object of interest. In the case of a tracker which employs an IR (infrared) sensor, the tracker will usually lock onto and track the warmest feature or spot on the object. For example, if the object is a moving vehicle with internal propulsion, the hotspot position (track point) does not necessarily coincide spatially with a desirable aimpoint on the object since desirable aimpoints usually reside on the main body of the object and are dependent on the goals of the task.
In order to achieve such an aimpoint, the entire outline or silhouette of the object, or at least a major portion of it, must be extracted from the background. This process of extraction, which is referred to as "segmentation" by the image processing fraternity, is generally considered to be one of the most difficult and challenging problems encountered in the design of systems which employ image processing technology.
The difficulty of segmentation is a result of the presence in the field of view of one or more interference or confusion factors which cause the object of interest to be either incompletely segmented or occluded by interfering objects, or "clutter". Compounding the problem further is the inevitable presence of noise. In addition to these interferences, some sensors produce a form of noise known as "fixed pattern noise", which results from detector-to-detector nonuniformities in gain and d.c. offset.
Each of these problems requires its own particular solution, and quite often conflicts arise between the various remedies. For this reason, it is necessary to provide techniques whose purposes are to determine which segmentation process is appropriate to a given situation or set of conditions in the real world. Techniques of this type have the function of evaluating the scene content in order to quantitatively assess the levels of clutter and noise.